Short circuit locator apparatus including a plurality of intermittently operated circuit breakers

ABSTRACT

A method and apparatus for locating short circuits, primarily in a vehicle, which comprises of placing a pair of test leads across the defective fuse in a shorted circuit, the test leads being connected to a plurality of circuit breakers through a selector switch for selecting one of the circuit breakers. A relay in parallel with the selected circuit breaker operates a switch which controls a light and tone generator, such that when the circuit breaker is placed across the fuse terminals of a shorted circuit, an audible and visual signal will be generated by the tone generator and light.

United States Patent Smith, Jr.

154] SHORT CIRCUIT LOCATOR APPARATUS INCLUDING A PLURALITY OFINTERMITTENTLY OPERATED CIRCUIT BREAKERS [72] Inventor: Raymond PeterSmith, Jr., P.O. Box

294, South Williamsport, Pa. 17701 [22] Filed: Nov. 24, 1970 [21] App].No.: 92,388

[52] US. Cl ..324/52, 340/250, 340/253 A [51] Int. Cl. ..G0lr 31/08 [58]Field of Search ..324/51, 52, 115; 340/250, 255,

[56] References Cited UNITED STATES PATENTS 3,158,713 l1/1964 Margulies..340/250 3,074,013 1/1963 Bowden ..340/255 X 1,262,103 4/1918Schweitzer ..324/51 2,976,484 3/1961 McClain ..340/250 X 3,356,93912/1967 Stevenson ..324/51 3,263,164 7/1966 Solgere ..324/51 2,789,2364/1957 Cummings ..324/51 X 3,514,694 5/1970 Beachley ..324/51 2,581,3081/1952 Smith ..340/250 X [151 3,699,433 1 Oct. 17, 1972 2,039,267 4/1936Barber ..324/115 X 2,716,216 8/1955 Schwenzfeier; ..324/52 X 3,204,9239/1965 Rynders et a1. ..337/79 X 3,530,337 9/1970 Moore ..340/253 A X3,621,384 11/1971 Yamada ..324/52 FOREIGN PATENTS OR APPLICATIONS767,558 2/1957 Great Britain ..324/52 234,592 6/1925 Great Britain..340/253 A Primary ExaminerGerard R. Strecker Attorney-Sughrue,Rothwell, Mion, Zinn & Macpeak [57] ABSTRACT A method and apparatus forlocating short circuits, primarily in a vehicle, which comprises ofplacing a pair of test leads across the defective fuse in a shortedcircuit, the test leads being connected to a plurality of circuitbreakers through a selector switch for selecting one of the circuitbreakers. A relay in parallel with the selected circuit breaker operatesa switch which controls a light and tone generator, such that when thecircuit breaker is placed across the fuse terminals of a shortedcircuit, an audible and visual signal will be generated by the tonegenerator and light.

6 Claims, 2 Drawing Figures 32 34 26 TONE GENERATOR SHORT CIRCUITLOCATOR APPARATUS INCLUDING A PLURALITY OF INTERMITTENTLY OPERATEDCIRCUIT BREAKERS BACKGROUND OF THE INVENTION 1. Field of the InventionThis invention relates to a method and apparatus for the location ofshort circuits and more particularly to placing an apparatus with aplurality of circuit breakers across the fuse terminals of a shortedcircuit such that an audible and visual signal are generated so long asthe short circuit exists.

2. Description of the Prior Art In prior art devices a plug was insertedin place of a defective fuse in a shorted circuit and an audible orvisual indication was given until the short circuit was fixed. In thisarrangement a large current due to the short circuit could burn out thecircuit wiring as well as the audible and visual indicators.Furthermore, the operator of the device had no indication as to thecharacter of the short circuit.

SUMMARY OF THE INVENTION When a short circuit occurs in an automotiveelectrical circuit the fuse in that circuit usually burns out. In themethod and apparatus of this invention two test leads are placed acrossthe terminals of the defective fuse. One of the test leads is connectedto a bus bar and the other is connected to a rotary switch for selectingone of a plurality of thermal type circuit breakers. One side of thecircuit breakers is connected to the rotary switch and the other side isconnected to the bus bar. A relay is connected in parallel with theseries circuit of the selector switch and selected circuit breaker insuch a manner that when the thermal type circuit breaker opens due tothe short circuited current through it, the relay will operate to closea switch. The relay operated switch is connected to audible and visualindicators, such that upon operation of the switch the indicators givetheir respective indications. The short circuit may be located byplacing the test leads across the defective fuse terminals of theshorted circuit and selecting an appropriate thermal type circuitbreaker. The breaker is selected in accordance with the rated value ofthe defective fuse or the wire gauge in the shorted circuit. This willcause an audible and visual signal to be given by the indicator devices.The short is then located by the operator physically moving along thecircuit separating the wires or by moving along the wirewith a probelessammeter. With the ammeter the point of highest current is the locationof the short. When the short circuit is located and fixed the audibleand visual indication will cease, because there will no longer besufficient current through the thermal type circuit breaker to open thatbreaker, thereby energizing the relay which causes the operation of theaudible and visual indicators.

An ammeter is provided which may be connected into said shorted circuitso the operator will be given some indication as to the nature of theshort circuit. For example, if the short is made by a large area of barewire touching the chassis of an automobile and making a good connectionwith the chassis, then a large short circuit current will be drawnthrough the ammeter. If, on the other hand, the short is caused by asmall amount of wire barely touching the chassis of an au- It is also anobject of this invention to provide a method and apparatus for thelocation of short circuits in which the operator may determine thenature of the short circuit which he is trying to locate.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 shows a circuit diagram of thepreferred em bodiment of the present invention.

FIG. 2 shows the exterior of the preferred embodiment of this invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to FIG. 1, test lead A:is connected to selector switch 2 which is used to select one of thethermal type circuit breakers 4 14. The circuit breakers are allconnected to bus bar 16. Test lead B is connected to the fuse terminalB. Selector switch 18 is connected to test lead B through line 20.Selector switch 18 is used to select between ammeter 22 and circuitbreakers 4 14 when testing a shorted circuit. Lamp 24 and relay coil 26are connected between bus bar 16 and test lead A.

When test leads A and B are connected to fuse terminals A and B andselector switch 18 is set so that an appropriate one of the thermal typecircuit breakers 4 are placed in the circuit, current flows from oneterminal of the vehicle battery through the short circuit throughselector switch 18, bus bar 16, to the selected circuit breaker 10 asshown in FIG. 1. Current flows through the circuit breaker throughselector switch 2 and then to the other terminal of the vehicle batterywhich is connected to terminal A through the shorted circuit. Whencircuit breaker 10 has heated up, it will open, thereby causingsufficient current to flow through relay 26 to operate that relay. Sincethe circuit breaker 10 is then open, no current will flow through it andit will cool down, reclosing the circuit through selector switch 2 andthereby cutting off current through relay 26. This, therefore, producesan intermittent current through relay 26.

When current flows through relay 26 it operates switch 30, therebycausing current to flow through lamp 32 and tone generator 34. Power issupplied to lamp 32 and tone generator 34 from power supply 36 which isseparate from the vehicle power supply. As can readily be seentherefore, the intermittent current through relay 26 intermittentlyoperates switch 30, causing lamp 32 to give a flashing indication forthe existence of a short circuit and further causing tone generator 34to give an intermittent audible indication for the short circuit. Whenselector switch 18 is in a position to connect ammeter 22 across testleads A and B, the operator of this invention will be given anindication of the current flowing in the short circuit and this cuit.

Referring nowto FIG. 2, the apparatus of this invention is housed incase 38. On the front face of case 38 are selector switches 2 and 18,ammeter 22, and indicator lamps 24 and 32. Extending from case 38 aretest leads A and B. On the side of case 38 is an opening 40 for emittingsounds from tone generator 34. The apparatus further includes selectorswitches 42 and 44 for selecting the frequency and volume of tonegenerator 34.

When operating this device, selector switch 2 is set at a valuecorresponding to the rated value of the defective fuse or to the gaugeof the wire in the shorted circuit. The operator then places test lead Aonto one terminal of the fuse terminals of the shorted circuit and testlead B on the other fuse terminal. Selector switch 18 is placed in theposition for operating ammeter 22 and the operator checks the reading ofthe ammeter to determine the current flowing in the shorted circuit.This gives him an indication of the nature of the short circuit. Ifthere is a large current this is indicative of the fact that there is alarge short in the circuit. This might, for example, be a bare wiretightly pressed against the chassis of the automobile. On the otherhand, if there is a low current this is indicative of the fact that theshort is small, such as a slightly bared wire lightly pressing againstthe chassis of the automobile. Since the operator knows the nature ofthe short for which he is looking, his task in finding the short will begreatly simplified. After determining the amount of current in theshorted circuit, switch 18 is then moved to the circuit breakerposition, at which time lamp 32 begins flashing and an audible signal isemitted from opening 40. The operator then physically begins moving thewires of the shorted circuit away from the chassis of the automobile.When the short circuit is reached and is separated from the chassis ofthe automobile the short will be opened and a lamp 32 will stop flashingand tone generator 34 will stop emitting an audible tone. As previouslystated, the operator will be able to tell the nature of the short forwhich he is looking by noting the current through ammeter 22.

While the invention has been particularly shown and described withreference to the further embodiment thereof, it will be understood bythose skilled in the art will aid him in determining the nature of theshort cirthat various changes in form and detail may be made thereinwithout departing from the spirit and scope of the invention.

What is claimed is:

1. An apparatus for locating shorts in an electrical circuit including aprotective means comprising:

a. first and second test lead means for connecting said apparatus acrosssaid protective means;

b. a plurality of intermittently operating circuit breakers, eachcircuit breaker connected to said first test lead means and opening andclosing in response to a different magnitude of current therethrough;

c. selector switch means connected between said second test lead meansand said plurality of circuit breakers for selecting one circuit breakerfrom said plurality;

d. switch means connected between said first and second test lead meansand in parallel with said selected circuit breaker for conducting thecurrent between said test lead means when said one circuit breakeropens, with the resistance of said switch means being high relative tothe resistance of said selected circuit breaker; and

e. indicator means connected'to said switch means for operating inresponse to the operation of said switch means.

2. The apparatus of claim 1 wherein each circuit breaker is a thermaltype whereby when the current exceeds the rated value of said circuitbreaker said circuit breaker opens and after cooling closes in a cyclicaction, thereby causing an intermittent current to flow through saidswitch means.

3. The apparatus of claim 2 wherein said switch means comprises a relay.

4. The apparatus of claim 1 wherein said indicator means comprises bothan audible and visual indicator.

5. The apparatus of claim 1 further including ammeter means connectedacross said first and second test leads means for indicating themagnitude of the current flowing in the shorted circuit.

6. The apparatus of claim 3 wherein said indicator means comprises anaudible and visual indicator; and further including ammeter meansconnected across said first and second test lead means for indicatingthe magnitude of the current flowing in the shorted circuit.

1. An apparatus for locating shorts in an electrical circuit including aprotective means comprising: a. first and second test lead means forconnecting said apparatus across said protective means; b. a pluralityof intermittently operating circuit breakers, each circuit breakerconnected to said first test lead means and opening and closing inresponse to a different magnitude of current therethrough; c. selectorswitch means connected between said second test lead means and saidplurality of circuit breakers for selecting one circuit breaker fromsaid plurality; d. switch means connected between said first and secondtest lead means and in parallel with said selected circuit breaker forconducting the current between said test lead means when said onecircuit breaker opens, with the resistance of said switch means beinghigh relative to the resistance of said selected circuit breaker; and e.indicator means connected to said switch means for operating in responseto the operation of said switch means.
 2. The apparatus of claim 1wherein each circuit breaker is a thermal type whereby when the currentexceeds the rated value of said circuit breaker said circuit breakeropens and after cooling closes in a cyclic action, thereby causing anintermittent current to flow through said switch means.
 3. The apparatusof claim 2 wherein said switch means comprises a relay.
 4. The apparatusof claim 1 wherein said indicator means comprises both an audible andvisual indicator.
 5. The apparatus of claim 1 further including ammetermeans connected across said first and second test leads means forindicating the magnitude of the current flowing in the shorted circuit.6. The apparatus of claim 3 wherein said indicator means comprises anaudible and visual indicator; and further including ammeter meansconnected across said first and second test lead means for indicatingthe magnitude of the current flowing in the shorted circuit.